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A key conference on the use of email authentication to fight spam concluded in Washington last week without any clear conclusions on which approach will gain market acceptance.

The Federal Trade Commission (FTC) and the Director of the National Institute of Standards and Technology (NIST) Email Authentication Summit took place on Tuesday and Wednesday last week and coincided with an Internet Engineering Task Force Meeting, also in Washington. During the FTC’s summit various proposals for email authentication were outlined.

Sender Policy Framework and Sender ID are both designed to verify the domain from which email has been sent and therefore minimise spoofing. Both involve checking the IP address of a server originating email against a list of servers a domain owner allows to send email. Sender ID is Microsoft's approach to spam-busting protocols, which dropped the idea of embedding XML in DNS records from its earlier Caller ID proposal.

Microsoft's restrictions on sublicensing Sender ID led the IETF to rebuff the proposal last month. However many anti-spam firms are supporting the technology, so Sender ID is sill important to the market - despite the reservation of the net's technical governing body. "There's been a lot of infighting in the IETF between SPF and Microsoft supporters," said Matt Sergeant, senior anti-spam technologist at email filtering firm MessageLabs. "Open source advocates, and others, don't want to see Bill Gates becoming the 800lb gorilla that controls the technology for blocking junk mail."

Other proposals discussed last week incorporate the use of digital signature technology. DomainKeys involves the use of digital signatures in email messages. These digital signatures allow recipients of email to verify that messages were sent from the claimed email address and to verify that messages have not been tampered with. Yahoo!, which developed the technology, began using the technique within its email service yesterday.

Another approach to fighting spam and phishing using cryptographic techniques comes via Cisco's Identified Internet Mail technology. Cisco, supported by other vendors and end users, reckon path-based and signature-based approaches in the fight against spam are complementary but the many different proposals under discussion all contribute to a somewhat confusing picture.

Emerging identity standards, including DomainKeys, Sender ID and SPF, are welcome additions to the arsenal of weapons in the fight against spam, but they are not a "silver bullet", anti-spam firm Habeas says. From next year on businesses that want to get their email reliably delivered will need to adopt these standards as part of their email practices, it says. But which approach should users embrace?

It is unclear which of the many proposals for email authentication will become dominant. The FTC Summit had done little to clarify this, MessageLabs' Sergeant notes. "At the moment the industry is in a holding pattern. Email authentication is a large undertaking, still at the experimental stage, and I reckon it'll be at least six months before a clear direction emerges. It could be that Sender ID and SPF will split into two rival camps," he said. ®